In the past two decades, studies in Caenorhabditis elegans, Drosophila melanogaster and Mus musculus have identified G protein-coupled receptors (GPCRs) expressed on olfactory sensory neurons (OSN) as putative odorant receptors [4–8]. Imaging and electrophysiology studies in flies and mice have revealed that odorant molecules can bind multiple receptors, thus activating different sensory neurons in the olfactory epithelium [9–11]. Interestingly each sensory neuron expresses only one kind of receptor and all neurons expressing the same receptor project to the same glomerular target in the olfactory bulb [8,12,13]. These studies suggest that olfactory cues might be spatially represented in the olfactory bulb. However, less is known about their representation in higher order brain regions.